Visible crew/equipment: In the scene where Brody approaches the group of teenagers on their smashed boats, the angle cuts to show Brody approaching seen as if from Cable Junction. At this point, there is a huge mistake. The teenagers' boats are clearly visible in the foreground, the kids have all completely vanished, and you can spot the cameraman standing on the boats quite clearly.
Continuity mistake: When Brody thinks he spots a shark, he rings his bell, then begins to descend the watch tower. In one shot you can see a woman with blonde hair, sitting on a beach-chair, at the bottom of the watch-tower. In the next overhead shot, as Brody runs across the beach, the same woman now suddenly has an orange hat on.